Patients with schizophrenia and Tourette's disorder are compared to normal controls with respect to the uptake of the dopamine neurotransmitter-dependent tracer 6-18F-DOPA by positron emission tomography (PET). PET allows quantification and localization of tissue radionuclide content with high spatial resolution. 6-18F-DOPA, an analogue of L-DOPA allows in vivo visualization of dopamine and its metabolites in the areas of the brain believed to be involved in schizophrenia and Tourette's disorder. Patients are being studied on and off neuroleptics. The scans are analyzed by comparing regions of interest (ROI), and by utilizing metabolite analysis based on the Patlack model. So far, 14 normal controls, 11 schizophrenic patients and four Tourette's syndrome patients have been studied. Preliminary data show a significant increase in uptake in the schizophrenic group on neuroleptics.